Rotatable chair height-adjustment mechanism



C. R. HELMS June 4, 1968 ROTATABLE CHAIR HEIGHT-ADJUSTMENT MECHANISM 2 Sheets-Sheet 1 Filed Aug. 2, 1966 INVENTOR Q. Rosem Hews fw new ATTORNEY c. R. HELMS 3,386,697

ROTATABLE CHAIR HEIGHTADJUSTMENT MECHANISM June 4, 1968 2 Sheets-Sheet 2 Filed Aug 2, 1966 INVENTOR. C. ROBERT HEUMS BY Jab-aw. M,

United States Patent 3,386,697 ROTATABLE CHAIR HEIGHT-ADJUSTMENT MECHANISM Charles Robert Helms, East Greenville, Pa., assignon to Knoll Associates, Inc., New York, N.Y., a corporation of New York Filed Aug. 2, 1966, Ser. No. 569,641 6 Claims. (Cl. 248-406) ABSTRACT OF THE DISCLOSURE In a swivel-chair height-adjustment mechanism for adjusting the height of a chair seat relative to a chair base, including a hub connected to the chair base, a column telescopingly received within the hub and connected to the chair seat, a spindle mounted for rotation within the hub and having a helical thread on the exterior thereof, a nut connected to the column having a thread engaged with the spindle thread to support the chair seat on the chair base, and means for selectively locking the spindle against rotation relative to the chair base, the improvement, in combination with the foregoing, comprising an indentation (depression or aperture) in each of a number of turns of the spindle thread, and a detent portion of the nut thread protruding downwardly toward the chair base and essentially parallel to the nut thread axis disposed to engage within an indentation in the spindle thread. In a preferred form the nut thread detent portion includes a downwardly convex surface integrally formed by deformation of the nut thread.

Background of the invention Swivel-type chairs, such as oflice chairs having a base and an upwardly extending column on which the chair seat is mounted for swiveling movement, desirably include a height-adjustment mechanism so that the chair seat may be adjusted to each occupant. Typical height-adjustment mechanisms include exposed parts, e.g. generally a threaded spindle and a handwheel, which are unsightly and which also can snag or dirty the clothing of the occupant. Sometimes the chair must be turned on its side to have its height adjusted, and in other cases the occupant must bend or stoop to work the adjustment handwheel. In recent years, design trends and the commercial requirements of the market have demanded chairs whose outline is unmarred by such exposed mechanical parts. What is desirable in the art is a height-adjustment mechanism for swivel-type chairs in which all the mechanical parts are hidden from view within the normal contours of the chair, and also, in which adjustment of the chair height can be eifected without stooping or bending by the occupant, and while the chair is in the normal upright position.

It is an object of the invention to provide an improved height-adjustment mechanism of simplified and compact construction.

Another object of the invention is to provide a heightadjustment mechanism in which the height adjusting elements are substantially entirely enclosed within the normal chair outline.

Another object of the invention is to provide an economical height-adjustment mechanism which may be sirn ply and efliciently adjusted while the operator is in the standing postion.

For a better understanding of the invention, reference may be had to the following detailed description and the accompanying drawings, in which:

FIG. 1 is a front elevational view of a chair support including the improved height adjustment mechanism of the invention;

3,386,597 Patented June 4, 1968 FIG. 2 is an enlarged sectional view on the line 2-2 of FIG. 1 and shows details of the height-adjustment mechanism;

FIG. 3 is a perspective view of a single thread nut shown in section in FIG. 2;

FIG. 4 is a sectional view on the line 4-4 of FIG. 2;

FIG. 5 is a sectional view on the line 5-5 of FIG. 2;

FIG. 6 is a sectional view on the line 66 of FIG. 2; and

FIG. 7 is a fragmentary sectional view corresponding to that of FIG. 2 but showing an orientation of adjustment elements during height adjustment.

Referring now to the figures, a chair seat 1 (shown in fragmentary form in FIG. 1) is swivel-mounted to a chair base 2. A height-adjustment mechanism 7 according to the invention is situated intermediate chair seat 1 and chair base 2, below a tubular column 8 connected to the chair seat 1, and substantially entirely within a tubular hub 9 connected to chair base 2. The swivel action is provided by the telescoped tubular members 8, 9 which. are respectively connected to the chair seat 1 and chair base 2. The height-adjustment mechanism 7 according to the invention selectively holds the column 8 at a fixed height and against axial displacement While permitting rotation for swiveling action of the chair seat 1 relative to the hub 9, or causes the column 8 to move axially upwardly or downwardly with rotation relative to the hub 9 for changing the height of the chair seat 1 relatively to the base 2.

The chair seat 1 may be rigidly connected to the column 8; preferably, however, a chair control mechanism 3 is partly attached to the chair seat 1 and] partly attached to the column 8 to provide tilting movement of the chair seat 1 relative to the column 8 and the base 2. The chair control mechanism 3 includes a pan bracket 5a which is rigidly secured by suitable means such as screws 6 to a pan 5 which may be considered the chair seat, but which often further supports padding or the like, so that chair seat 1 is shown generally as including the pan 5 and its seating appurtenances. The chair control mechanism 3 is pivotally connected to the column 8 at the pan bracket 5a. The chair control mechanism 3 yieldingly opposes tilting movement of the chair seat 1 relative to the column 8 and includes a handwheel 4 for adjusting its initial yielding opposition to tilting movement.

Any suitable chair control mechanism may be employed with the height-adjustment mechanism according to the present invention; however a tension control mechanism having features which render it particularly advantageous for use in cooperation with the height-adjustment mechanism 7 of the invention is shown and claimed in my copending patent application, Ser. No. 569,640, entitled Chair Control, filed concurrently herewith.

FIG. 1 clearly illustrates the compactness of the heightadjustment mechanism of the invention and its harmonious relationship with the chair seat 1 and base 2. It is also apparent that the component elements of the mechanism of the invention which are necessary to its proper funcice tioning and which provide for the selective swiveling or height-adjustment operations, are substantially enclosed and concealed from view, whereby the mechanism is fully adaptable to use with any chair design without spoiling the outline thereof.

In the sectional view of FIG. 2, there is shown only a lower portion of the column 8, defining a. hollow housing 60. A pair of axially separated annular insteps 5t) and 53 are formed on the column 8, the instep 50 preferably being formed at an intermediate axial position and the instep 53 being formed adjacent the lower end of the column 8. Annular bushing rings 54 and 55 are received within the insteps 50 and 53, respectively, and serve as radial hearings to maintain the column 8 in coaxial relationship within the hub 9 While permitting relative rotation and axial displacement therebetween.

A spindle 61 is mounted for rotation within the hub 9. The spindle 61 includes an upper portion having a spiral thread 70, a reduced diameter axle 62 and lug 63 having flat edge surfaces, the axle 62 and lug 63 projecting axially downwardly from the upper portion of the spindle 61. A base plate 64 is received within the bottom end of the tubular hub 9 and secured thereto, preferably by welding, as indicated at 65. The base plate 64 includes a central aperture 66 within which a bearing 67 is received, the bearing 67 including a thin walled cylindrical portion 67a received within the aperture 66 and a thicker-walled annular flange portion 67b which rests on the upper surface of the base plate 64. Preferably, a flat annular washer 68 is positioned on the upper surface of the flange portion 67b. The spindle 61 is positioned with the upper, threaded portion resting on washer 68, the axle 62 extending through the apertured bearing 67 and the lug 63 projecting downwardly from the lower surface of base plate 64.

The thread 70 is cut in the outer surface of the spindle 61 and extends from the hub 62 in a spiral until portion 70a is reached near the top of spindle 61. Portion 78a extends thread 70 vertically upward to the top of spindle 61. Portion 78a performs two functions. First, it forms a stop for nut 75 upon raising of seat 1. Second, it allows the seat 1, with column 8 and nut 75 to be easily removed (or replaced) by raising the seat 1 until portion 70a: is abutted by nut 75, and then lifting (or lowering, as the case may be) the seat 1 with column 8 off of or onto spindle 61 and base 2. A pair of channels 72 are cut through the thread 70, preferably in axially aligned relationship on diametrically opposite sides of the spindle 61, and orthogonal to thread portion 70a. The channels 72 extend through the entire radial depth of the thread 70 and partially into the solid cylindrical surface of the spindle 61. In effect, the channels 72 represent indentations in successive turns of spindle thread 70. While it is preferred to have these indentations be full apertures in the thread 70, and further to have these apertures aligned into channels, they can also be depressions instead of apertures in spindle thread 78, and they need not be aligned from turn to turn.

A single threaded nut 75 is welded to the bottom end of column 8, as indicated at 76, and is received on the thread 70 of spindle 61 to support the column 8 on the spindle 61. The nut 75 is best shown in the perspective view of FIG. 3 and conveniently may be stamped from a steel washer of annular configuration. The inner portion of the annular washer is cut, as at 77 and bent to define a generally spiral, single thread 78 having the same pitch as the spiral thread 70 on spindle 61. Detents 79 are formed in diametrically opposite portions of the nut thread 78. Both nut detents protrude downwardly, i.e. in a downward direction parallel to the nut thread axis. The downward protrusion gives an additional locking effect when the chair seat is loaded. The total thickness of nut 75, including the depth of protrusion of each nut detent 79, is slightly less than the axial spacing between the upper face of one turn and the lower face of the adjacent turn of the spiral thread 70 of the spindle 61, and the width of each nut detent 79 is slightly less than the width of the spindle channels 72. As illustrated in FIGS. 2 and 4, the detents 79 are receivable in the channel 72 between the spaced ends of each thread 70 parted by the channel, the remainder of the generally spiral portion of the thread 78 of the nut 75 resting on a turn of the spiral thread 70 of the spindle 61.

A latch 80 is provided for selectively locking the spindle 61 to the hub 9 for restraining relative rotation therebetween. The latch 80 includes a locking plate 81 which, referring concurrently to FIGS. 2 and 5, includes a gen- .4 erally rectangular, centrally disposed aperture 82 by which the plate 81 is slidingly received on the lug 63 of spindle 61. The locking plate 81 includes a number of protrusions 85 disposed in equiangular positions at a constant radius on the upper one of its planar surfaces. In the illustrated embodiment, protrusions 85 comprise round headed cy lindrical pins. A retainer ring 83 is received in channels 84 cut into the opposite sides of the lug 63 and retains the locking plate 81 on the lug 63.

Referring concurrently to FIGS. 2 and 6, the base plate 64 includes a number of apertures 86 disposed in equiangular relationship and at the same radius as that of the protrusions 85. Each of the apertures 86 is sufliciently large to receive an associated one of the protrusions 85 thereby to positively lock the locking plate 81 against rotational motion relative to the base plate 64.

As one alternative, the protrusions 85 and apertures 86 may be interchanged in whole or in part such that the locking plate 81 contains apertures such as 86 and the base plate 64 contains protrusions such as 85, but extending downwardly. As a further alternative, a single eccentric protrusion and a single, similarly eccentric aperture may be employed in place of the plurality of protrusions 85 and aperture 86, respectively, to provide locking of the locking plate 81 to the base plate 64.

In operation, the column 8 is locked to the spindle 61 for common rotation relatively to the hub 9, to thereby provide swivel-action of the chair at constant height. As discussed above, the detents 79 of nut 75 are normally received in the vertical channels 72; the weight of the occupant of the chair, transmitted through the column 8 and supported on the nut 75, securely locks the detents 79 within the channels 72. The nut 75 therefore tightly engages the spindle 61, and the column 8 and the spindle 61 rotate in common on the thrust bearing 67 to provide the aforesaid normal swivel-action of the chair seat 1. The radial bearings 54 and allow for the swivel-action while maintaining column 8 in proper axial alignment with the column 9.

To adjust the chair height, the spindle 61 is selectively locked against rotation to the hub 9 by operation of the latch 80. The locking plate 81 may be raised by the tip of ones shoe to engage the protrusions 85 within the apertures 86 of the base plate 64. This can be accomplished without stooping, and is advantageous; however the operation can be effected by hand if desired. Although it may well occur that the protrusions 85 are not initially aligned with the apertures 86 during the application of an upwardly directed force to the plate 81, upon swiveling of chair seat 1, the protrusions 85 will be rotated into alignment with, and will be inserted into the apertures 86 and thus will lock the spindle 61 to the hug 9.

Once the spindle 61 is locked to the hub 9, continued rotation of the chair seat effects the height-adjustment. This occurs because a torque is developed between nut 75 and spindle 61, which causes the detents 79 to be withdrawn from their locked relation in channels 72 by riding out of channels 72 and onto spindle thread 70. Thus, simply by raising lock plate 81 and turning chair seat 1, the nut 75 is caused to ride the thread thereby causing raising or lowering of seat 1. The riding-out of the detents 79 may be seen in progress in FIG. 7. As noted previously, the depth of the detents 79 is such that the thread 78 and the detents 79 may ride within the spacing of the threads 70 of the spindle 61, and thereby advance the nut axially along the spindle 61. Every half-turn of rotation, the detents 79 will reengage channels 72, but if the locking plate 81 is kept up, they will ride right out again under partly turning of chair seat 1. The heightadjustment is thus continuously variable in one-half turn increments. The extent of displacement of the nut 75 is limited by the unthreaded portion 71 at the top of the spindle 61 and the washer 68 at the bottom of the spindle 61.

The operation of the latch is obviously an extremely simple task which does not even require the plate 81 to be touched by hand. Nevertheless, a secure locking of the spindle 61 to the hub 9 is achieved. The ability to change the height of the chair seat by the simple expedient of rotating the chair seat while the latch 80 is engaged is highly advantageous, since the dimensions of the chair seat in every case afford a lever arm of a sufficient length to render the rotating of the nut 75 on the spindle 61 a substantially effortless operation. It has been found that in oflices, particularly when the operator is female, the feature of adjustment without stooping and without using the hands to work mechanical parts, is highly approved.

The height-adjustment mechanism 7 of the invention provides a compact, low cost, and highly effective support for chairs, and is particularly advantageous for use with ofiice chairs. The component elements of the mechanism are substantially enclosed and concealed from view, enhancing the appearance of the mechanism and reducing any tendency of the mechanism to collect dust and dirt. The avoidance of collecting dust and dirt also contributes to smoother operation and prolonged life of the mecha msm.

The tubular column 8, which supports the chair seat 1, is free to rotate within hub 9 during swiveling, and is free to telescope in and out of hub 9 during heightadjustment, without scoring or abrasion of its surface. This is important from the standpoint of appearance, and also because the surface need not be lubricated and is thus more acceptable since it cannot dirty the clothes of the user.

Numerous other advantages and modifications and adaptations of the invention will be readily apparent to those skilled in the art, and it is intended by the appended claims to cover all such modifications and adaptations which fall within the true spirit and scope of the invention.

What is claimed is:

1. A swivel-chair height-adjustment mechanism for adjusting the height of a chair seat relative to a chair base comprising:

(a) a hub connected to said chair base;

(b) a column telescopingly received within said hub and connected to said chair seat;

(0) a spindle mounted for rotation within said hub and having a helical thread on the exterior thereof, and an indentation in each of a number of turns of said thread, the axis of said helical thread being disposed vertically when said swivel-chair is in the normal upright operative position;

((1) a nut connected to said column, including a nut thread engaged with said spindle thread to support said chair seat on said chair base, said nut thread having a detent portion protruding toward said chair base in the general direction of said helical thread spindle axis, said detent portion being thereby disposed to engage, under the urging of the weight carried by said nut, within any said indentation in the particular spindle thread turn upon which said nut thread rests, but to be releasable therefrom upon the application of torque between said nut and spindle sufficient to overcome said weight; and

(e) means for selectively locking said spindle against rotation relative to said chair base, so that when so locked, torque may be applied between said chair seat and base to develop torque between said nut and said spindle up to the amount of torque required to force said detent away from said chair base out of said indentation against any weight carried by said nut to free said nut for threaded movement up or down said spindle.

2. A swivel-chair height-adjustment mechanism for adjusting the height of a chair seat relative to a chair base comprising:

(a) a hub connected to said chair base;

(b) a column telescopingly received within said hub and connected to said chair seat;

(0) a spindle mounted for rotation within said hub and having a helical thread on the exterior thereof, and an indentation in each of a number of consecutive turns of said thread, the axis of said helical thread being disposed vertically when said swivelchair is in the normal upright operative position;

(d) a nut connected to said column, including a nut thread engaged with said spindle thread to support said chair seat on said chair base, said nut thread having a detent portion integrally formed therein protruding toward said chair base in the general direction of said helical thread spindle axis, said detent portion being thereby disposed to engage, under the urging of the weight carried by said nut, within any said indentation in the particular spindle thread turn upon which said nut thread rests, but to be releasable therefrom upon the application of torque between said nut and spindle sufficient to overcome said Weight; and

(e) means for selectively locking said spindle against rotation relative to said chair base, so that when so locked, torque may be applied between said chair seat and base to develop torque between said nut and said spindle up to the amount of torque required to force said detent away from said chair base out of said indentation against any weight carried by said nut to free said nut for threaded movement up or down said spindle.

3. A swivel-chair height-adjustment mechanism for adjusting the height of a chair seat relative to a chair base comprising:

(a) a hub connected to said chair base;

(b) a column telescopingly received within said hub and connected to said chair seat;

(c) a spindle mounted for rotation Within said hub and having a helical thread on the exterior thereof, and an indentation in each of a number of consecutive turns of said thread at the same circumferential position to form a column of indentations in the thread periphery, the axis of said helical thread being disposed vertically when said swivel-chair is in the normal upright operative position;

(d) a nut connected to said column, including a nut thread engaged with said spindle thread to support said chair seat on said chair base, said nut thread having a detent portion integrally formed therein to include a convex surface protruding toward said chair base in the general direction of said helical thread spindle axis, said detent portion being thereby disposed to engage, under the urging of the weight carried by said nut, within any said indentation in the particular spindle thread turn upon which said nut thread rests, but to be releasable therefrom by application of torque between said nut and spindle sufiicient to progressively force said. detent portion away from said chair base by action of said convex surface on the spindle thread portion adjacent said indentation against the weight carried by said nut until said detent portion is fully removed from said indention; and

(e) means for selectively'locking said spindle against rotation relative to said chair base, so that when so locked, torque may be applied between said chair seat and base to develop said sufficient torque between said nut and said spindle.

4. A mechanism according to claim 2, wherein said indentations in said spindle thread occur in essentially diametrically opposed pairs, the indentations comprise apertures, and the opposed pairs of indentations being arranged in two columns essentially parallel to the helical axis of said spindle; and wherein said nut includes an essentially diametrically opposed pair of said detents adapted to engage any of said diametrically opposed pairs of spindle thread indentations.

5. A mechanism according to claim 1, wherein said means for selectively locking said spindle against rotation relative to said chair base comprises first means located underneath said chair base and rotatable with said spindle, and second means spaced upwardly of said first means in opposition thereto and secured to said chair base, one of said first and second means including at least one protrusion facing the opposed of said said means, and the other of said first and second means including a depression positively matable with said protrusion.

6. A mechanism according to claim 5, wherein said first means comprises a spindle plate rotationally fixed to, but axially movable with respect to, said spindle, including a plurality of pins arranged on a constant radius and facing upwardly, and a fixed plate secured to said 8 chair base including a plurality of apertures spaced to receive said pins, said spindle plate being axially movable upwardly and downwardly sufiiciently to allow insertion and withdrawal of said pins in said apertures.

References Cited UNITED STATES PATENTS ROY D. FRAZIER, Primary Examiner.

R. P. SEITTER, Assistant Examiner. 

